The present invention relates to a steering column of a motor vehicle. More specifically, the present invention relates to a steering column mounting system and method for absorbing energy in the steering column of a motor vehicle.
When a motor vehicle is involved in a collision, the driver of the motor vehicle may forcefully impact the steering wheel. In order to reduce the force of this impact, a conventional steering column may be controllably collapsible. More specifically, when the driver impacts the steering wheel in a collision, the steering column partially collapses so as to absorb some of the impact force.
One example of a conventional energy-absorbing steering column support system is shown and described in U.S. Pat. No. 6,170,873 entitled xe2x80x9cSteering Column Mounting Bracket with Pull Loopsxe2x80x9d and includes a mounting bracket having a steering column extendable therethrough. The mounting bracket has four slots through which the bracket is secured to the structure of the motor vehicle by fasteners, e.g., bolts or capsules. A frictional force of the fasteners in the slots prevents the steering column from collapsing until an impact force of the driver against the steering wheel overcomes the frictional force and causes the fasteners to slide within the slots, thereby absorbing some of the impact. In addition, the mounting bracket has a pair of resilient, but bendable, U-shaped pull loops associated with a lower two of the slots. A first end of each pull loop has a hole through which extends the fastener associated with the slot, while a second end of the pull loop is free to move. When a collision occurs and the impact force of the driver against the steering wheel causes the fastener to move within the slot, the U-shaped pull loop is caused to unwind. Since the pull loops are resiliently bendable, the unwinding of the pull loop is resisted, thereby absorbing some of the energy and reducing the force of the impact of the driver against the steering wheel.
While conventional steering column mounting systems provide some energy absorbing capabilities, they typically rely on frictional forces to maintain the steering column in its initial position prior to collision. These frictional forces may also be present while the steering column is moving during a collision and may reduce the effectiveness of the steering column in absorbing energy during a collision.
Thus, there is a need to provide a steering column mounting system and method that provides improved effectiveness in absorbing energy during a collision.
It is therefore an object of the present invention to provide a steering column mounting system and method that provides improved effectiveness in absorbing energy during a collision.
It is another object of the present invention to provide a system and method that provides adequate friction forces to maintain a steering column in its initial position prior to a collision.
It is another object of the present invention to provide a system and method that substantially reduces the friction forces present in the steering column mounting system when the steering column is moving during a collision.
The above and other beneficial objects of the present invention are achieved by providing a system and method as described herein. The present invention, according to one example embodiment thereof, relates to a steering column mounting system that includes a mounting bracket fixedly attached to a steering column and at least one pull strap made of a resiliently bendable material. The pull strap has a first leg with a slot. Extending through the slot is a fastener fixedly attached to a motor vehicle structure. The pull strap also has a free second leg substantially parallel to the first leg. Upon relative movement between the mounting bracket and the fastener, e.g., upon a driver impacting the steering column during a collision, the pull strap is caused to unwind.
The pull strap may have two or more unwinding portions having different widths. The widths of the portions of the pull strap may be selected so as to provide a predetermined amount of resiliency to the unwinding portions of the pull straps. The widths of the portions of the pull strap may also be selected so as to provide differing amounts of resiliency at different stages of the unwinding of the pull straps. A support frame is attached to the mounting bracket and maintains the first leg and the second leg of the pull strap substantially parallel relative to each other during the unwinding of the pull strap.
The mounting bracket may also include a slot through which extends the fastener fixedly attached to a motor vehicle structure. The mounting bracket may have a tapered, e.g., decreasing, cross-section over a length of the slot. In this manner, a frictional force between the fastener and the mounting bracket, which is sufficient to maintain the position of the fastener relative to the mounting bracket prior to a collision, is substantially reduced when the fastener is caused to move from a first end of the slot to a second end of the slot during a collision.